Seven Toyo and Vietnam Sunergy Companies Ask the Northern District of California to Declare Their TOPCon Solar Products Do Not Infringe Two First Solar Patents.

The case is Toyo Co., Ltd. v. First Solar, Inc., No. 5:26-cv-10832 (N.D. Cal.), filed September 23, 2026. The plaintiffs are Toyo Co., Ltd.; TOPTOYO Investment Pte. Ltd.; Toyo Solar Manufacturing One Member Private Limited Company; Toyo Solar Texas LLC; VSUN Solar USA Inc.; Vietnam Sunergy Joint Stock Company; and Vietnam Sunergy (Bac Ninh) Company Limited. The complaint describes them as affiliated companies that make TOPCon solar cells in Ethiopia and modules in Texas for the U.S. market and sell modules through VSUN Solar USA.

The patents and the ITC investigation

The patents are U.S. Patent 9,130,074, issued September 8, 2015, and U.S. Patent 9,666,732, issued May 30, 2017, both titled High-Efficiency Solar Cell Structures and Methods of Manufacture. The complaint says the '732 patent is a division of the '074 patent and that First Solar claims to own both.

According to the complaint, First Solar filed an ITC complaint on February 24, 2026 in Certain TOPCon Solar Cells, Modules, Panels, Components Thereof, and Products Containing Same, Inv. No. 337-TA-1494, alleging that the plaintiffs' TOPCon cells and modules, including the Vesta N and TYMN lines, infringe claims 1, 2, 4, and 8 of the '074 patent, and seeking a general exclusion order covering all TOPCon cells and modules, and a limited exclusion order and cease and desist order against the plaintiffs. The complaint says First Solar has moved to dismiss the investigation without prejudice and, in a September 15, 2026 press release attached as Exhibit A, said it would continue its district court TOPCon suits against other manufacturers and anticipated filing more.

The non-infringement claims

The complaint seeks declarations that the plaintiffs do not infringe any claim of either patent, directly or indirectly. It says their TOPCon products are not made using the methods of independent claim 1 of the '074 patent, which recites depositing a doped conductive and passivating layer on an interface passivation layer, thermal treatment at about 500 degrees C or higher that crystallizes the layer and diffuses the dopant, and metallization contacting the layer, or independent claim 1 of the '732 patent, which recites forming the interface passivation layer by thermally treating an amorphous silicon-containing compound with oxygen and conductive dopants. It also asks for a finding that the case is exceptional and for attorneys' fees, and demands a jury.

What to watch next

The docket shows the summons returned executed on October 27, 2026, a clerk's notice of impending reassignment on October 28, and a reassignment and a clerk's notice setting a Zoom hearing on October 29. Watch for First Solar's response, including any infringement counterclaims. The case can end at any time, including by settlement or voluntary dismissal.